Quote from: TheNineClub on Today at 10:52:42 AM

<...> I never got why you would have to achieve a certain rank before posting pictures, makes not much sense to me.

It looks like a requirement that was originated in september 2015 due to abuse of some sort at the time:

Quote from: theymos on September 06, 2015, 08:35:15 PM

Due to abuse, newbie-posted embedded images are now disabled on these pages:
- Topic display
- Recent posts / patrol
- Previews
They're not currently hidden in PMs or on some other pages (like a user's "show posts" page), though I might change that later if it seems necessary.

Disabled images get transformed into links automatically. When the poster becomes a Jr member, the images that he tried to post previously will automatically be re-enabled (though there might be a few minutes of delay).

This extends to all past posts as well as future ones.

Although back then, reaching Jr. Member rank was trivial (only based on Activity), since September 2018 it also required having earned at least 1 Merit (see Enhanced newbie restrictions & requirements).

Quote

<...> Is there any way to make it mandatory to read posts like this before starting on the forum? Like right after registration?

Well, quite a bit of the content is on the Help Menu (see https://bitcointalk.org/index.php?action=help;page=post), which is where one would expect to go to if needed.